Phase shift apparatus adjustable by movement of dielectric slug



June 4, 1963 c. F. AUGUSTINE ETAL 3,092,793

PHASE SHIFT APPARATUS ADJUSTABLE BY MOVEMENT OF DIELECTRIC SLUG FiledSept. 28, 1959 32 fini lllsllh e se Hg. 2

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-' CARROLL R AuGusTlNE JAMES cHEAL E g 4 BY vlNcENT J. Mc HENRY ATTORNEY3,092,793 PHASE SHIFT APPARATUS ADJUSTABLE BY MOVEMENT F DIELECIRIC SLUGCarroll F. Augustine and Vincent J. McHenry, Farmington, and JamesCheal, Inkster, Mich., assignors to The Bendix Corporation, acorporation of Delaware Filed Sept. 28, 1959, Ser. No. 842,966 12Claims. (Cl. 333-31) rIhis invention pertains to a phase shift apparatusand, more particularly, to an apparatus for shifting the phase of asignal in a linear ratio to an input motion.

It is an object of this invention to provide a phase shift apparatus ofa small size and rugged construction which has a linear relation betweeninput movement and phase shift, which requires relatively low drivingtorque for operating the input member and is capable of performing overa very wide range of frequencies.

I-t is an object of this invention rto provide 1a phase shift apparatusincluding a helix of coaxial cable 'which has the outer cable conductor'and a portion of the cable insulation removed along the inner helixsurface so that the inner cable conductor can come into `a closeregistration with -a cylindrical member or slug -as it is inserted inthe helix to vary the ydielectric constant of the helix andcorrespondingly change the phase of the signal in the helix.

These and other objects will become more apparent when .a preferredembodiment of this invention is considered in connection with thedrawing in which:

FIGURE 1 is a partially schematic view of a helix with a plug partiallyinserted therein;

FIGURE 2 is a section taken ralong 22 of FIG- URE l;

FIGURE 3 is an elevational view of the coaxial cable s'hfwing thetapered cut-away of the removed portion; an

FIGURE 4 is a section taken along 4 4 of FIG- URE 3.

In the drawing there is shown `a coaxial cable 20 having outer conductor22, inner conductor 24, and insulation 26 therebetween. The coaxialcable 20 may be a miniature 50 ohm cable which has an outside diameterof .085 inch with the `dielectric 26 being of polytetrailouroethyleneresin available from Du Pont under the trade name Teonf The cable hasthe outer conductor 22 and a portion of the insulation 26 removed alonga side thereof for a predetermined distance, .thereby placing the innerconductor 24 near the insulation surface. Satisfactory results are ralsoobtainable when .the insulation 26 is cut away suiiiciently to exposeinner conductor 24. The outer conductor 22 is cut away at a taper 28both at the beginning and end of the removed portion. The cable 20 isthen closely wound about a cylindrical mandrel (not shown) or othermeans so that the removed cable portions are facing inwardly of thehelix 30. The outer conductor 22 of the individual coils of helix 30 aresoldered together while the inner conductor 24 of the coils of helix 30are insulated from one another fby i11- sulation 26. The helix in thisembodiment is 2.25 inches long and has an inner diameter of .450 inch.

A slug 32 having a tapered end 34 is inserted into helix 30 and has, inthis embodiment, a clearance of about .002 inch with the inside helixdiameter. The taper 34 on the inserted end of slug 32 effects a betterimpedance match. The slug preferably has a dielectric constant of l andla loss tangent of .001. The clearance is preferably small so that the'high dielectric constant slug will have the maximum effect on thefields around the exposed inner or center conductors 24.

A screw 36 is attached to the upper end of slug 32 United States PatentO 3,092,793 Patented June 4, 1963 rice and is turned by motor 38 throughgear reducer 40. Controls lare available on motor 38 to insert slug 32 adesired distance into helix 30. Insertion of the slug 32 into helix 30changes the dielectric constant of the helix and this correspondinglychanges the phase of the signal in the helix. The degree of phase shiftcorresponds in linear relation to .the insertion length of slug 32 inhelix 30.

In the -above embodiment phase shift can 'be provided for a wide band ofsignals, for example from 400 megacycles to 6 kilomegacycles. The totalphase shift for 1.8 inches of slug penetration is 490 at 2.97 kmc. andis linear to within plus or minus 3. Maximum insertion loss at 3 kmc. isless than 2 decibels. lIf lower loss is desired, a slug formed of Aliteor aluminum oxide of equivalent properties can be used. Also, by using aslug of high loss matreial a compact variable -attenuator is provided.

Although this invention has been disclosed and illustrated withreference to particular applications, :the principles involved .aresusceptible of numerous other applications which will be :apparent topersons skilled in the The invention is, therefore, to Ibe limited onlyas indicated by the scope of the appended claims.

Having thus described our invention, we claim:

1. A phase shifter comprising a coaxial cable having a center conductor:and a coaxial shield for said center conductor with insulationtherebetween, -a circumference sector of said cable having yapredetermined portion of the shield removed, .a dielectric member havinga predetermined idielectric constant movable in increments relative saidconductive member to cover a total length of said conductive membercorresponding to said total movement and movable in close proximity Itosaid circumference sector of said cable having said shield portionremoved, so that the flux lines from one portion of said member aresubstantially shielded from other portions of said conductive member butare Unshielded lfrom said flux modifying member.

2. r[The phase shifter of claim 1 wherein said circumference sector ofsaid cable having the shield portion removed also has a predeterminedportion of said insulation removed.

3. The phase shifter of claim 2 wherein said cable is formed in a helixwith the circumference sector of said cable having the shield andinsulation removed facing the center of the helix and forming asubstantially smooth shaftway through the center of said helix, saiddielectric member being cylindrical in shape and movable through andclose fitting with said shaftway.

4. The phase shifter of claim 2 wherein said shield .and insulation .areremoved sufciently so that said d-ielectric member is spaced apredetermined distance from said center conductor of said coaxial cable.

5. An attenuator comprising a coaxial cable having a center conductorand a coaxial shield with insulation therebetween, a circumferencesector of said cable having a predetermined portion of the shieldremoved, a high loss member having a predetermined loss characteristicmovable in increments relative said conductive member to cover a totallength of said conductive member corresponding to said total movementand movable in close proximity to said circumference sector of saidcable having said shield portion removed, so that the ux lines from oneportion of said member are substantially shielded from other portions ofysaid conductive member but are Unshielded from said ilux modifyingmember.

6. The attenuator of claim 5 wherein said circumference sector of saidcable having the shield portion removed also has la predeterminedportion of said insulation removed.

7. The` attenuator of claim 6 wherein said cable is formed' in a helixwith the circumference sector of said cable having the shield andinsulation removed facing the and close tting with said shaftway.

8. The yattenuator of claim 6 wherein said shield yand insulation areremoved sufliciently so Vthat said high loss member is4 spaced apredetermined distance from said center conductor of said coaxial cable.

, 9. Apparatus comprising f la 'conductive member adapted :to carry asignal to be modified,

said conductive member being electrically shielded l:abou-tja`predetermined portion of its cross sectional f circumference andUnshielded about the remaining portion of its circumference,

a member :havingp'redetermined flux modifying characteristics movable inclose proximity to the unshielded portion of sa-id conductive member,

said ux modifying member movable in increments relative'said conductivemember to cover a total length of said conductive member correspondingto the total movement, I

lthe ux lines from said shielded portion of said conductive member beingconned within said-shieldy ing and substantially all of the flux linesof the unf [shielded portions Ycovered by the ytotal length of said iluxmodifying member entering said flux/modifying member.

10. The `apparatus of claim 9 wherein said :ux modifying member issemi-conductive.

11. The vapparatus of claim 10 wherein the portion shielded is at least`as large as the portion that is unshielded.

12. The Iapparatus of claim 11 wherein said yconductive-member is formedin a helix with saidnnsh-ielded portion being Ion the inside of thehelix,

said semi-conductive flux modifying member being movable through thecenter of said helix closelyiadjacent said unshielded portion.

References Cited in the le of this patent UNITED STATES PATENTSV2,419,907 M016 Apr. 29, 1947 Y 2,454,530V vTiley Nov. 23, 1948 72,507,358 Waggoner M-ay 9, 1950 '2,512,945 Kallmann June 27, 19502,527,608 Y `Will0ugl1by 'Oot. 31, 1950 2,636,148 Gorham Apr. 21, 19532,811,696 e Berkley Oct. 29, 1957 2,908,746 Fairhlllst Oct. 13, 19592,951,999 Marchese Sept. 6, 1960 2,993,140 `Westbrook July 18, 19613,031,632 Krakau et al. Apr. 24, 1962 FOREIGN PATENTS 130,561 AustraliaMay 2 1946 632,834 Great Britain Dec. 5, 1949

1. A PHASE SHIFTER COMPRISING A COAXIAL CABLE HAVING A CENTER CONDUCTORAND A COAXIAL SHIELD FOR SAID CENTER CONDUCTOR WITH INSULATIONTHEREBETWEEN, A CIRCUMFERENCE SECTOR OF SAID CABLE HAVING APREDETERMINED PORTION OF THE SHIELD REMOVED, A DIELECTRIC MEMBER HAVINGA PREDETERMINED DIELECTRIC CONSTANT MOVABLE IN INCREMENTS RELATIVE SAIDCONDUCTIVE MEMBER TO COVER A TOTAL LENGTH OF SAID CONDUCTIVE MEMBERCORRESPONDING TO SAID TOTAL MOVEMENT AND MOVABLE IN CLOSE PROXIMITY TOSAID CIRCUMFERENCE SECTOR OF SAID CABLE HAVING SAID SHIELD PORTIONREMOVED, SO THAT THE FLUX LINES FROM ONE PORTION OF SAID MEMBER ARESUBSTANTIALLY SHIELDED FROM OTHER PORTIONS OF SAID CONDUCTIVE MEMBER BUTARE UNSHIELDED FROM SAID FLUX MODIFYING MEMBER.